An Evaluation of the Effectiveness of An Evaluation of the - PowerPoint PPT Presentation

An Evaluation of the Effectiveness of An Evaluation of the Effectiveness of School Zone Flashers School Zone Flashers Carrie Simpson, PE Carrie Simpson, PE Prepared By: Prepared By: Safety Evaluation Group Safety Evaluation Group NCDOT Traffic Engineering NCDOT Traffic Engineering

Current Practice Current Practice Flashers are currently being placed on many school zone signs throughout North Carolina at the request of schools and in an attempt to bring more awareness to the speed limit signs. Current NC Administrative Code (Title 19A Chapter 2 Subchapter B) “ Standard signing and marking for school zones is the responsibility of the Department of Transportation. If a traffic and engineering investigation conducted by the Department of Transportation shows that there are hazardous conditions present adjacent to a school greater than those normally present in school areas, and that these conditions can be alleviated by the use of school flashers, then the Department of Transportation will install school flashers and maintain them.”

Report Objectives Report Objectives This report summarized the effectiveness of placing flashers on school zone speed limit signs to improve speed compliance in school zones Our objectives were to: • Determine if flashers located in reduced speed school zones decrease speeds and increase speed compliance when compared to reduced speed school zones without flashers. • Examine differences in vehicle speeds and compliance rates in school zones during reduced speed school zone hours of operation (school time) versus hours outside the reduced speed school zone hours of operation (non-school time).

Sign and Flasher Assemblies Sign and Flasher Assemblies All treatment sites contained dual flashers that were either mounted on a pole on the side of the roadway (11 sites) or on span wire above the roadway (4 sites). Western Alamance High Pleasant Garden Elementary

Measures of Effectiveness Measures of Effectiveness – Percent of vehicles exceeding the speed limit – Average vehicle speed – 85 th percentile speed – Pace speed Speed data measured in the morning and afternoon on typical weekdays when school was in session during: • School Time at treatment sites, • Non-School Time at treatment sites, • School Time at comparison sites, and • Non-School Time at comparison sites.

Site Selection Site Selection • Contacted Regional Traffic Engineers to create a statewide listing of candidate flasher sites • Compiled a list of over 120 candidate sites spanning from Division 5 to 14 • Used the TEAAS ordinance system to identify comparison non-flasher sites that matched the treatment sites as closely as possible • Scheduled field visits to locations that had been installed at least 3 years and were within a reasonable driving distance from Raleigh

Site Selection Site Selection FINAL SELECTION: • 15 treatment sites with flashers • 15 comparison sites without flashers • Sites with a mix of geometric and geographic features • School time speed limits between 25- 45 mph

Comparison Sites Comparison Sites Speed data from the treatment and comparison sites were compared during non-school time hours to measure how similar the two groups operated. The data shows that the treatment and comparison sites are similar, with the same speed distributions during non-school time hours. The comparison sites are a good comparison group without any conditions that would reasonably affect a driver’s choice of speed. Speed Data Collected During Non-School Time Hours (With Speeds Referenced From the Non-School Time Speed Limit)

Results - Flasher vs. Non-Flasher Results - Flasher vs. Non-Flasher Speed Distribution During School Time Similar Distribution 450 •The flashers are not more effective at 400 See Report Flasher Locations lowering vehicle Non-Flasher Locations Page 7 350 speeds than signing Number of Vehicles 300 alone. 250 Low Compliance • At treatment and 200 comparison sites, 150 average and 85th 100 percentile speeds are 50 approx. 6 mph and 12 mph above the 0 -40 -30 -20 -10 0 10 20 30 40 speed limit. Observed Speed Minus School Time Speed Limit

Results - School Time vs. Non-School Time at Non-Flasher Locations Results - School Time vs. Non-School Time at Non-Flasher Locations Shifted Distribution Figure 4. Speed Distribution at Non-Flasher Locations •School time speed During School Time and Non-School Time distribution is 450 See Report noticeably shifted to the School Time 400 Page 9 Non-School Time left from the non- 350 school time speed 300 distribution. Number of Vehicles Speed Decrease 250 •Vehicle speeds 200 decreased from non- 150 school time hours to school-time hours at 100 non-flasher sites. 50 •Average vehicle 0 speeds below the non- -40 -30 -20 -10 0 10 20 30 40 Observed Speed Minus Non-School Time Posted Speed Limit school time speed limit.

Results - School Time vs. Non-School Time at Flasher Locations Results - School Time vs. Non-School Time at Flasher Locations Shifted Distribution Speed Distribution at Flasher Locations During School Time and Non-School Time •Vehicle speeds 500 decreased from non- See Report School Time 450 school time hours to Non-School Time Page 8 400 school-time hours at 350 flasher sites. Number of Vehicles 300 Flashers and Non- 250 Flashers Behaved 200 Similar 150 •Overall, the speed 100 distributions of both 50 flasher and non- 0 flasher sites appear -40 -30 -20 -10 0 10 20 30 40 very similar during all Observed Speed Minus Non-School Time Posted Speed Limit times of day.

Crash Analysis Crash Analysis • For completeness, analyzed crash rates at all sites using the most recent 3 years of reported crashes • Due to small sample sizes difficult to draw conclusions from data FINDINGS: • Crash rates were higher at flasher sites than non-flasher sites during both school time hours and non-school time hours • At flasher and non-flasher sites, approximately 30 percent of crashes are occurring during school time hours • No pedestrian crashes occurred during school time hours.

Conclusions Conclusions • Flashers are not more effective at lowering speeds in school zones than signing and pavement marking alone. • Regardless of flasher presence, average speeds during school time were above the school time speed limit but below the non-school time speed limit. This indicates that motorists were making an effort to reduce their speed during the school time, although the speed reductions were not enough to bring them into compliance with the school time speed limit.

QUESTIONS? QUESTIONS?